1. Field of the Invention
The present disclosure relates to a communication system, and in particular, but not exclusively, to allocation of resources, for example, scheduling of data packets in a communication system providing wireless communication for users thereof.
2. Description of the Related Art
A communication system can be seen as a facility that enables communication sessions between two or more entities such as user equipment and/or other nodes which are a part of or are otherwise associated with the communication system. The communication may comprise, for example, communication of voice, data, multimedia and so on. A user equipment connected to a communication system may, for example, be provided with a two-way telephone call or multi-way conference call or with a data connection. A user equipment may communicate packet data to and from a server entity, between two or more user equipments or otherwise on the interface between the user equipment and the communications system.
A communication system typically operates in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. For example, the standard or specification may define if a user equipment is provided with a circuit switched service or a packet switched service or both. Communication protocols and/or parameters which shall be used for the connection are also typically defined. For example, the manner how the user equipment can access the communication system and how communication shall be implemented between the user equipment and the elements of the communication network is typically based on predefined communication protocols. In other words, a specific set of “rules” on which the communication can be based on needs to be defined to enable the user equipment to communicate via the communication system.
Communication systems proving wireless communication for user equipment are known. These systems are commonly referred to as mobile systems, although in certain systems the mobility may be restricted to substantially small areas. An example of the mobile systems is the public land mobile network (PLMN). A PLMN is commonly based on cellular architecture. Another example is a mobile system that is based, at least partially, on use of communication satellites. Mobile communications may also be provided by means of other mobile systems, such as by means of wireless local area networks (WLAN). The mobile users are commonly enabled to roam into networks other than the networks they subscribe to, and therefore common standards and protocols are essential for wireless communication systems offering mobility.
In a common wireless system a base station servers a plurality of user equipment. A user equipment may also be in wireless communication with two or more base stations at the same time. Communication on the wireless interface between the user equipment and the base station can be based on an appropriate communication protocol. The skilled; person knows the basic operational principles and elements required for the wireless access to the network. Examples of these include access systems such as the CDMA (Code Division Multiple Access), WCDMA (Wide-band CDMA), TDMA (Time Division Multiple Access), FDMA (Frequency Division Multiple Access), or SDMA (Space Division Multiple Access) and hybrids thereof.
Each base station is controlled by an appropriate control arrangement. The operation of a base station and other apparatus for the communication can be controlled by one or several control entities. Two or more base stations may be controlled by a controller. For example, the third generation (3G) Wideband Code Division Multiple Access (WCDMA) networks employ control entities known as radio network controllers (RNC) for controlling the operation of the wireless access network. A WCDMA radio network controller typically controls a number of stations, and often all stations, of an access network.
The access network controllers are connected to core network entities. One or more gateway nodes may also be provided for connecting a communication network to other networks. For example, a mobile network may be connected to communication networks such as an IP (Internet Protocol) and/or other packet data networks.
As mentioned above, a user equipment may communicate data over a wireless interface with the access system. When a user equipment has sufficient amount of data to transmit in a buffer thereof some capacity needs to be allocated to the user equipment by the access system, and more particularly, air interface capacity is required from the base station.
A base station may receive substantially simultaneously a number of capacity allocation requests from different user equipment. Due to the limitations in the resources available over the air interface the base station may need to be able to allocate the capacity to those user equipments which should, for reason or another, transmit data with higher priority. In other words, the base stations may need to be able to prioritize transmission by the user equipment before allocating capacity for data transmissions.
Conventionally the prioritization has been provided by mapping different services onto dedicated channels with different priority amongst the channels. The packet scheduling functionality in the network side is located at the radio access network controller level, such as the RNC of the WCDMA. This has been a fairly straightforward solution since for example in the WCDMA the radio network controller (RNC) is aware about the priorities of the different radio bearers on the so called the Medium Access Control d (MAC-d) layer.
In certain applications it is possible to multiplex data carried on different radio bearers with different priorities into one transport channel. For example, wireless communication between a user equipment and a base station can be signaled on an Enhanced Dedicated Channel (E-DCH) at the mobile terminal Medium Access Control e (MAC-e) layer. This layer is hierarchically a lower level layer than the above mentioned MAC-d, and is only used by the user equipment and the base station.
The above mentioned method of mapping different services onto dedicated channels with different priorities is not considered optimal in the case of technologies such as the E-DCH where fast packet scheduling is done at the base station (called Node B in the WCDMA) and the available E-DCH resources must be shared with other users in a shared channel fashion.
In High Speed Downlink Packet Access (HSDPA) this problem is solved by using Scheduling Priority Indicator (SPI) associated with different bearers from the RNC to the Node B. However this solution cannot always be applied to E-DCH, for example because the quality indicators cannot be signaled explicitly at the layer 1 of the protocol stack due to limited resources available to the signaling.
Therefore there is a need for an improved solution for scheduling of data transmission on the wireless interface in the access network base station level.